The flat panel display apparatus has many advantages such as thinness, power saving and radiation-free etc., and thus being used widely. The flat panel display apparatus in the related art primarily comprises Liquid Crystal Display (LCD) apparatus and Organic Light Emitting Diode (OLED) display apparatus.
The OLED display apparatus realizes displaying by self-luminance, and thus it needs no backlight, and has excellent characteristics such as high contrast, small thickness, wide view angle, rapid response, capable of being manufactured as a flexible display panel, wide range of operating temperature, and simple configuration and process, regarded as the next generation display apparatus which can displace the LCD.
OLED display apparatus can be classified into two categories, i.e., Passive Matrix OLED (PMOLED) display apparatus and AMOLED display apparatus, in terms of the driving mode, that is, Direct Addressing and Thin Film Transistor (TFT) Array Addressing. Thereinto, the PMOLED display apparatus is generally used as small-size display apparatus, since the power consumption of the PMOLED display apparatus is higher, which obstacles its application in large-size display apparatus. The AMOLED display apparatus is generally used as large-size display apparatus with high definition due to its high light-emitting efficiency.
FIG. 1 is a circuit diagram of a pixel circuit of an AMOLED display apparatus in the related art. In the display area of the AMOLED display apparatus, the pixels are arranged in a matrix form including a plurality of rows and a plurality of columns, and each pixel is generally driven using a pixel circuit constituted of two thin film transistors and one capacitor, that is, using the driving mode of 2T1C. Specifically, the gate of the first transistor T1 is electrically connected to the gate line Scan, the source is electrically connected to the data signal line DATA, and the drain is electrically connected with the gate of the second transistor T2 and one terminal of the capacitor C; the source of the second transistor T2 is electrically connected to the high voltage signal terminal VDD, and the drain is electrically connected to the anode of the organic light emitting diode D; the cathode of the organic light emitting diode D is electrically connected to the common ground electrode VSS; one terminal of the capacitor C is electrically connected to the drain of the first transistor T1, and the other terminal is electrically connected to the source of the second transistor T2. When displaying, the gate line Scan controls the first transistor T1 to be turned on, the data signal voltage of the data single line DATA is supplied to the gate of the second transistor T2 and the capacitor C through the first transistor T1, and then the first transistor T1 is turned off, and the gate voltage of the second transistor T2 can still continue maintaining the data signal voltage due to the effect of the capacitor C, such that the second transistor T2 is in the on-state, the driving current of the high voltage signal terminal VDD corresponding to the data signal voltage is supplied to the organic light emitting diode D through the second transistor T2, and the organic light emitting diode D is driven to emit light.
In the AMOLED display apparatus described above, the organic light emitting diode D is driven depending on the current generated by the second transistor T2 in the saturated state; and since the critical voltages of the second transistors T2 in respective pixels are not the same due to the nonuniformity in the TFT process, and since different extent of drift will occur in the threshold voltage Vth of the second transistor T2 during the light emission of the organic light emitting diode D, the brightness uniformity in respective pixel is poor when been driven with the above-mentioned 2T1C driving circuit, resulting in disadvantages such as the display nonuniformity and the like.